JP5083477B2 - Manufacturing method of glass substrate for information recording medium - Google Patents

Description

  The present invention relates to a method for producing a glass substrate for information recording medium and a glass substrate for information recording medium.

  With the increase in the density of information recording media, demands for glass substrates for information recording media are increasing, and smoothing and high cleaning are essential. This glass substrate for information recording media is generally manufactured through a lapping process. Conventionally, in the lapping process, the grinding apparatus is provided by using a grinding liquid using pure water as a solvent or by using a grinding apparatus having a function of separating polishing sludge components such as polishing scraps. Clogging of a grindstone as a grinding member is prevented (see Patent Document 1).

  If the grinding member becomes clogged, the frequency of dressing of the grinding member, such as diamond sheet, will increase, and the productivity will be reduced, as well as scratching the ground surface of the glass base plate (which refers to the workpiece during the glass substrate manufacturing process) This may cause quality degradation such as occurrence of cracks and poor flatness of the ground surface. Furthermore, the cost increases in order to promote the deterioration of the grinding member.

JP 2002-241742 A

  The present invention provides a method for manufacturing a glass substrate for an information recording medium that is less likely to cause clogging of the grinding member, is efficient, and has a low risk of quality deterioration, and an information recording medium manufactured by the manufacturing method. The purpose is to provide a glass substrate.

  One aspect of the present invention is a method for manufacturing a glass substrate for an information recording medium, which includes a lapping process in which a surface of a glass base plate is lapped using a grinding device provided with a grinding member and a grinding liquid, the lapping process Then, the grinding liquid is lapped so that the total content of calcium and magnesium is always 5 mg / L or less. This is a method for producing a glass substrate for an information recording medium.

  Another aspect of the present invention is a glass substrate for information recording medium manufactured by the method for manufacturing a glass substrate for information recording medium.

  Objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description and the accompanying drawings.

It is a perspective view of the glass substrate for information recording media manufactured by the manufacturing method of the glass substrate for information recording media concerning one embodiment of the present invention. It is process explanatory drawing for demonstrating the process of the manufacturing method of the glass substrate for information recording media which concerns on one Embodiment of this invention. It is explanatory drawing of the grinding device used for the lapping process of the manufacturing method of the glass substrate for information recording media which concerns on one Embodiment of this invention. It is the table | surface showing the result of the Example, (a) is the table | surface showing the result of the life test of the 1st diamond sheet in an Example, (b) is the result of the life test of the 2nd diamond sheet in an Example. It is a table showing.

  In the lapping process, if the grinding fluid contains calcium or magnesium, an insoluble metal salt is formed by the calcium or magnesium and the surfactant in the grinding fluid, and clogging of grinding members such as grindstones and diamond sheets. There is a risk of causing. In addition, even if a grinding fluid containing no or little calcium or magnesium is used, if a material containing calcium or magnesium is used as the glass substrate material, the calcium or magnesium component is contained in the grinding fluid during lapping. And an insoluble metal salt is generated by the calcium component or magnesium component and the surfactant in the grinding fluid, and as a result, there is a possibility of clogging the grinding member as described above. In such a case, even if a conventional grinding device having a sludge separation function is used, it is difficult to prevent clogging of the grinding member only by separating the generated sludge. The present invention has been completed as a result of such studies.

  Embodiments of the present invention will be described below. However, the present invention is not limited to this embodiment. FIG. 1 is a perspective view of a glass substrate 100 for information recording medium manufactured by the method for manufacturing a glass substrate for information recording medium according to this embodiment, and FIG. 2 is a manufacturing of the glass substrate for information recording medium according to this embodiment. It is process explanatory drawing for demonstrating the process of a method.

  In this embodiment, the method for manufacturing a glass substrate for an information recording medium includes a disk processing step, a lapping step, a rough polishing step, a chemical strengthening step, and a precision (finish) polishing step. The glass substrate 100 for information recording media is manufactured.

The glass material to be used is not particularly limited. For example, a glass composition containing silicon oxide (SiO ₂ ) as a main component and not containing both magnesium and calcium can be used. A glass composition containing one or both of magnesium and calcium can also be used. Furthermore, a glass composition containing no cerium or a glass composition containing cerium can also be used.

  A disk processing process is a process of processing the plate glass comprised from the glass raw material into a disk-shaped glass base plate. In this disk processing step, for example, a disk-shaped glass base plate having an outer diameter of 2.5 inches, 1.8 inches, 1 inch, 0.8 inches, etc. and a thickness of 2 mm, 1 mm, 0.63 mm, etc. is formed. Is done. The magnitude | size and thickness of the glass base plate formed by a disk processing process are not specifically limited.

As the glass workpiece, silicon oxide _(SiO 2): _55~75 wt%, aluminum oxide _{(Al 2} O 3): _5~18 wt%, lithium oxide _(Li 2 O): _1~10 wt%, sodium oxide (Na ₂ O): 3 to 15% by mass, potassium oxide (K ₂ O): 0.1 to 5% by mass (however, the total amount of Li ₂ O + Na ₂ O + K ₂ O: 10 to 25% by mass), magnesium oxide (MgO): 0.1 to 5 wt%, calcium oxide (CaO): 1 to 5 wt%, cerium oxide _(CeO 2): _0.1~5 wt%, zirconium oxide _(ZrO 2): _0~8 weight What consists of a glass raw material containing% is preferable.

  The lapping step is a step of processing the glass base plate into a predetermined plate thickness. In this embodiment, the lapping process is composed of two processes, a first lapping process and a second lapping process.

  In the first lapping step, both the front and back surfaces of the glass base plate are lapped to preliminarily adjust the overall shape of the glass base plate, that is, the parallelism, flatness and thickness of the glass base plate.

  In the second lapping step, the front and back surfaces of the glass base plate are again lapped to finely adjust the parallelism, flatness and thickness of the glass base plate.

  In this embodiment, for example, a grinding device capable of simultaneous grinding on both sides as shown in FIG. 3 is used as the grinding device 1 for lapping both front and back surfaces of the glass base plate in the first and second lapping steps. The grinding apparatus 1 includes an apparatus main body 1a and a grinding liquid supply unit 1b that supplies a grinding liquid to the apparatus main body 1a.

  The apparatus main body 1a includes a disk-shaped upper surface plate 2 and a lower surface plate 3 that are arranged at intervals in the vertical direction so as to be parallel to each other and rotate in opposite directions.

  A plurality of diamond sheets 4 for lapping both the front and back surfaces of the glass base plate 10 are attached to the opposing surfaces of the upper and lower surface plates 2 and 3. A plurality of rotatable carriers 5 are provided between the upper and lower surface plates 2 and 3.

  The carrier 5 is provided with a plurality of through holes 51. The glass base plate 10 is fitted into the through hole 51 and disposed. The upper and lower surface plates 2 and 3 can be operated by separate driving.

  The carrier 5 sandwiched between the surface plates 2 and 3 via the diamond sheet 4 rotates while maintaining a plurality of glass base plates 10 while lowering the surface plate 3 with respect to the center of rotation of the surface plates 2 and 3. Revolve in the same direction as. In the grinding apparatus 1 having such an operation, the grinding liquid 7 is supplied between the upper surface plate 2 and the glass base plate 10 and between the lower surface plate 3 and the glass base plate 10, respectively. The lapping of the glass base plate 10 can be performed.

  The diamond sheet 4 having a particle size of about 9 μm is used in the first lapping step, and that having a particle size of about 4 μm is used in the second lapping step.

  The grinding liquid supply unit 1 b includes a liquid storage unit 11 and a liquid recovery unit 12. The liquid storage part 11 includes a liquid storage part main body 11a and a liquid supply pipe 11b extended from the liquid storage part main body 11a to the apparatus main body 1a. The liquid supply pipe 11b has a discharge port 11e.

  The liquid recovery part 12 was extended from the liquid recovery part main body 12a, the liquid recovery pipe 12b extended from the liquid recovery part main body 12a to the apparatus main body part 1a, and the grinding liquid supply part 1b from the liquid recovery part main body 12a. And a liquid return pipe 12c.

  The grinding liquid 7 put in the liquid storage unit main body 11a is supplied to the apparatus main body 1a from the discharge port 11e of the liquid supply pipe 11b, and is recovered from the apparatus main body 1a to the liquid recovery unit main body 12a via the liquid recovery pipe 12b. Is done.

  The collected grinding liquid 7 is returned to the liquid storage part 11 via the liquid return pipe 12c, and can be supplied again to the apparatus main body part 1a. Therefore, the grinding fluid circulation path 6 of the grinding fluid supply part 1b is formed by the liquid storage part main body 11a, the liquid supply pipe 11b, the liquid recovery pipe 12b, the liquid recovery part main body 12a, and the liquid return pipe 12c.

  In this embodiment, the grinding fluid supply unit 1b includes a metal ion removal filter 8 in the middle of the grinding fluid circulation path 6 (in the illustrated example, the boundary between the fluid recovery unit main body 12a and the fluid return pipe 12c). The grinding liquid 7 passes through the metal ion removal filter 8 when circulating through the grinding liquid circulation path 6. During this passage, metal ions, such as calcium ions, magnesium ions, and cerium ions, contained in the grinding fluid 7 are removed by the metal ion removal filter 8.

  In this embodiment, the metal ion removal filter 8 is provided in the liquid recovery part main body 12a. When the grinding liquid 7 is returned from the liquid recovery part main body 12a to the liquid storage part main body 11a, metal ions are removed from the grinding liquid 7.

  In this embodiment, the grinding fluid 7 includes, for example, polyalkylene glycol, alkylene glycol monoalkyl ether, alcohol (such as methanol), fatty acid, nonion, and amines (such as monoethanolamine, diethanolamine, and triethanolamine). used.

  In the lapping process, the grinding fluid 7 is used while maintaining a state where the total content of calcium and magnesium is always 5 mg / L or less. If the total content of calcium and magnesium is 5 mg / L or less, clogging of the diamond sheet 4 as a grinding member is difficult to occur, and if it exceeds 5 mg / L, clogging of the diamond sheet 4 is likely to occur. is there. For example, before the start of the lapping step, a grinding solution in which the total amount of calcium and magnesium in the grinding solution is 5 mg / L or less can be adjusted, and the glass base plate can be lapped using this grinding solution.

  More preferably, the grinding fluid 7 is used while maintaining a total content of calcium and magnesium of 3 mg / L or less at all times. Thereby, it is possible to further prevent clogging of the diamond sheet 4. For example, before the start of the lapping step, a grinding solution in which the total amount of calcium and magnesium in the grinding solution is 3 mg / L or less can be adjusted, and the glass base plate can be lapped using this grinding solution.

  It is preferable that the grinding liquid 7 is used in the lapping process while the cerium content is always maintained at 10 mg / L or less. If the cerium content is 10 mg / L or less, clogging of the diamond sheet 4 as a grinding member is difficult to occur, and if it exceeds 10 mg / L, clogging of the diamond sheet 4 is likely to occur. For example, before the start of the lapping process, a grinding liquid in which the amount of cerium in the grinding liquid is 10 mg / L or less can be adjusted, and the glass base plate can be lapped using this grinding liquid.

  When the second lapping step is finished, the ground surface of the glass base plate 10 is free from defects such as large waviness, chipping and cracks, and the surface roughness of the surface of the glass base plate 10 is Rmax of 2 μm to 4 μm, Ra is preferably about 0.2 μm to 0.4 μm. By setting such a surface state, polishing can be performed efficiently in the next polishing step.

  After the first and second lapping steps, it is preferable to perform a cleaning step for removing the grinding members and glass powder remaining on the surface of the glass base plate 10.

  In the first and second lapping steps, when the grinding fluid 7 contains calcium, magnesium and / or cerium, they can be removed by the metal ion removal filter 8. Instead of the metal ion removal filter 8, or together with the metal ion removal filter 8, the grinding fluid 7 is used with water having a total calcium and magnesium content of 1 mg / L or less (hereinafter sometimes referred to as “dilution water”). By diluting, the amount of calcium and / or magnesium contained in the grinding fluid 7 may be maintained.

  For example, when diluting the grinding fluid 7 with diluting water during the lapping process, the calcium and magnesium contents of the grinding fluid 7 are periodically measured, and the total content of calcium and magnesium becomes 5 mg / L. It is better to dilute when it reaches 3 mg / L. Alternatively, a predetermined amount of the dilution water may be periodically added to the grinding fluid 7 without measuring the calcium and magnesium contents of the grinding fluid 7. By diluting the grinding fluid 7 with the dilution water, for example, during the lapping step, the total content of calcium and magnesium in the grinding fluid 7 can always be maintained at 5 mg / L or less or 3 mg / L or less. Further, the lapping process can be started from a state in which the total amount of calcium and magnesium in the grinding liquid 7 is very small by diluting the grinding liquid 7 with the diluting water before starting the lapping process, for example.

  The rough polishing step is a step of polishing the surface of the glass base plate 10 so as to improve the surface roughness to the extent that the surface roughness finally required in the precision polishing step described later can be efficiently obtained. .

  The rough polishing method is, for example, the first and second lapping processes except that a polishing pad and a polishing liquid (for example, those containing colloidal silica as an abrasive) are used instead of the diamond sheet and the grinding liquid used in the lapping process. It can be performed using a polishing apparatus having a configuration similar to that of the grinding apparatus used in the above.

  The chemical strengthening step is a step of forming a chemically strengthened layer on the glass base plate 10 by immersing the glass base plate 10 in the chemical strengthening treatment liquid. By forming the chemically strengthened layer, the impact resistance, vibration resistance, heat resistance and the like of the glass base plate 10 can be improved.

  In this chemical strengthening step, by immersing the glass base plate 10 in a heated chemical strengthening treatment liquid, alkali metal ions such as lithium ions and sodium ions contained in the glass base plate 10 are converted into potassium ions having a larger ion radius. It is carried out by an ion exchange method for substitution with alkali metal ions. Compressive stress is generated in the ion-exchanged region due to distortion caused by the difference in ion radius, and the surface of the glass base plate 10 is strengthened.

  The precision polishing step is a step of further precisely polishing the surface of the glass base plate 10 after the rough polishing step. The precision polishing process can be performed using a polishing apparatus having the same configuration as the polishing apparatus used in the rough polishing process, except that a polishing pad softer than the polishing pad used in the rough polishing process is used.

  After passing through the precision polishing step, a glass substrate 100 for an information recording medium as shown in FIG. 1 can be obtained through steps such as cleaning.

  The grinding device used in the first and second lapping steps, the polishing device used in the rough polishing step, and the precise polishing step are not limited to those in the above embodiment, and various devices can be used and can be changed as appropriate.

  In the above embodiment, the polishing liquid used in the rough polishing process and the precision polishing process contains colloidal silica as an abrasive. However, the present invention is not limited to this, and various types can be used and can be appropriately changed.

  As mentioned above, although one embodiment of the present invention was described in detail, the above-mentioned explanation is illustration in all the aspects, and the present invention is not limited to these. It is understood that countless variations that are not illustrated can be envisaged without departing from the scope of the present invention.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to this embodiment.

[Example 1]
A disk-shaped glass base plate having the following composition (hereinafter referred to as “glass base plate of composition 1”) was produced. The glass base plate of composition 1 is SiO ₂ : 64.5 mass%, Al ₂ O ₃ : 14.9 mass%, Li ₂ O: 3.6 mass%, Na ₂ O: 11.2 mass%, K ₂ O: 0.4 wt%, MgO: 0.6 wt%, CaO: 1.6 _wt%, CeO 2: _0.5% by _weight, ZrO 2: 2.0 _wt%, SnO 2: 0.7 wt% It consists of a glass material containing. Since the glass base plate of this composition 1 contains calcium, magnesium and cerium, calcium, magnesium and cerium of the glass base plate come out in the grinding liquid during the lapping process, and the amount of calcium in the grinding liquid, magnesium The amount of cerium increases.

In addition, a disk-shaped glass base plate (hereinafter referred to as “glass base plate of composition 2”) having the following composition was manufactured. Glass workpiece composition _2, SiO 2: 66.5 _{wt%, Al} 2 O 3: 14.1 _wt%, Li 2 O: 7.3 _wt%, Na 2 O: 3.0 wt%, _{K 2} O: 1.8% by mass, MgO: 2.4% by mass, CeO ₂ : 0.6% by mass, TiO ₂ : 1.9% by mass, Nb ₂ O ₅ : 2.4% by mass Is. Since the glass base plate of composition 2 contains magnesium and cerium, magnesium and cerium in the glass base plate come out into the grinding fluid during the lapping process, and the amount of magnesium and cerium in the grinding fluid increase. To do.

Furthermore, a disk-shaped glass base plate having the following composition (hereinafter referred to as “glass base plate of composition 3”) was produced. Glass workpiece composition _3, SiO 2: 63.6 _{wt%, Al} 2 O 3: 13.8 _wt%, Li 2 O: 5.7 _wt%, Na 2 O: 10.7 wt%, Sb ₂ It consists of a glass material containing O ₃ : 0.6 mass% and ZrO ₂ : 5.6 mass%. Since the glass base plate of this composition 3 does not contain calcium, magnesium, or cerium, the amount of calcium, the amount of magnesium, and the amount of cerium in the grinding liquid do not increase during the lapping process.

  Before starting the lapping process, by diluting the grinding fluid with water (dilution water) where the total amount of calcium and magnesium is 1 mg / L or less, the total amount of calcium and magnesium in the grinding fluid is 3 mg / L or less. A grinding liquid having an amount of 10 mg / L or less was prepared, and the produced glass base plates having compositions 1 to 3 were lapped using the grinding liquid. That is, while using the grinding apparatus provided with the metal ion removal filter shown in FIG. 3, during the lapping process, by diluting the grinding liquid with the dilution water according to the situation, the calcium and magnesium in the grinding liquid can be reduced. The glass base plates of compositions 1 to 3 were lapped so that the total amount was always 3 mg / L or less and the amount of cerium was always kept 10 mg / L or less.

  In the first lapping step, a diamond sheet having a particle size of 9 μm (hereinafter referred to as “first diamond sheet”) is used, and in the second lapping step, a diamond sheet having a particle size of 4 μm (hereinafter referred to as “second diamond sheet”) is used. did.

  As a result of performing lapping under the above conditions, the life of the first and second diamond sheets is shown in FIGS. 4 (a) and 4 (b). The life of the diamond sheet is the number (n) of the glass base plates that have been lapped before the diamond sheet becomes unusable (requires replacement). In the case of the first diamond sheet, it was determined that the glass base plate became unusable (end of life) when the flatness of the glass base plate reached an average value of 8 μm or more. FIG. 4A shows the number of glass base plates that have been lapped by that time (n = number of times of processing × number of times of processing of one time).

  In the case of the second diamond sheet, it was determined that the glass base plate became unusable (end of life) when the flatness of the glass base plate reached 7 μm or more on average. FIG. 4B shows the number of glass base plates that have been lapped by that time (n = number of times of processing × number of times of processing of one time).

  The flatness was measured with a flat nesting tester “FT-900” (manufactured by NIDEK) using a laser oblique incidence interferometer.

[Example 2]
The total amount of calcium and magnesium in the grinding fluid to be adjusted before the start of the lapping process is 3 mg / L and 5 mg / L or less. During the lapping process, the total amount of calcium and magnesium in the grinding liquid is always over 3 mg / L and 5 mg / L. A glass base plate having compositions 1 to 3 was lapped in the same manner as in Example 1 except that the following conditions were maintained. The results are shown in FIGS. 4 (a) and 4 (b).

Example 3
The total amount of calcium and magnesium in the grinding fluid to be adjusted before the start of the lapping process is set to 5 mg / L or less. During the lapping process, the total amount of calcium and magnesium in the grinding solution is always kept at 5 mg / L or less. A glass base plate having compositions 1 to 3 was lapped in the same manner as in Example 1 except that the amount was not controlled. The results are shown in FIGS. 4 (a) and 4 (b).

  Specifically, the amount of cerium was not controlled by using a metal ion removing filter that was adjusted so that calcium and magnesium were removed by adjusting the chelating agent but cerium was permeated.

  Therefore, the amount of cerium in the grinding fluid adjusted before the start of the lapping process was 10 mg / L or less. However, in the glass base plates of composition 1 and composition 2, the cerium contained in the glass base plate during the lapping step Appeared in the grinding fluid, and the amount of cerium in the grinding fluid gradually increased to exceed 10 mg / L (that is, the amount of cerium exceeded 10 mg / L during the lapping process). On the other hand, since the glass base plate of composition 3 does not contain cerium, the amount of cerium in the grinding fluid did not exceed 10 mg / L without controlling the amount of cerium.

[Comparative Example 1]
Before starting the lapping process, the grinding fluid was diluted with tap water instead of the dilution water, and the total amount of calcium and magnesium in the grinding fluid was always kept below 5 mg / L during the lapping process. In the same manner as in Example 1, glass base plates having compositions 1 to 3 were lapped. The results are shown in FIGS. 4 (a) and 4 (b).

  Specifically, the tap water used for diluting the grinding fluid had a total content of calcium and magnesium of 15 mg / L. Therefore, the total amount of calcium and magnesium contained in the grinding fluid adjusted before the start of the lapping process exceeded 5 mg / L. However, since the grinding fluid passes through the metal ion removal filter during the lapping process, the total amount of calcium and magnesium in the grinding fluid is 5 mg / L or less and the amount of cerium is 10 mg / L or less (that is, in the lapping process). Only in the initial stage, the total amount of calcium and magnesium exceeded 5 mg / L).

  From the results of FIGS. 4 (a) and 4 (b), calcium and magnesium are temporarily included in the grinding liquid during the lapping process because the total content of calcium and magnesium exceeds 5 mg / L. It seems that the generation of a surfactant and an insoluble metal salt such as a fatty acid and nonion clogged the first and second diamond sheets.

[Comparative Example 2]
The total amount of calcium and magnesium in the grinding fluid adjusted before the start of the lapping step was 5 mg / L or less, and the total amount of calcium and magnesium in the grinding solution was not controlled during the lapping step, as in Example 1. Then, a glass base plate having compositions 1 to 3 was lapped. The results are shown in FIGS. 4 (a) and 4 (b).

  Specifically, the total amount of calcium and magnesium was not controlled by using a metal ion removing filter that was adjusted so that cerium was removed by adjusting the chelating agent but calcium and magnesium were permeated.

  Therefore, the grinding fluid adjusted before the start of the lapping process has a total content of calcium and magnesium of 5 mg / L or less. However, in the glass base plate of composition 1, it is contained in the glass base plate during the lapping step. In the glass base plate of composition 2 with calcium and magnesium, the magnesium contained in the glass base plate during the lapping process is released into the grinding liquid, respectively, and the total amount of calcium and magnesium in the grinding liquid gradually increases. And the amount exceeded 5 mg / L (that is, the total amount of calcium and magnesium exceeded 5 mg / L from the middle of the lapping process). On the other hand, since the glass base plate of composition 3 contains neither calcium nor magnesium, the total amount of calcium and magnesium in the grinding fluid did not exceed 5 mg / L without controlling the total amount of calcium and magnesium. .

  From the results of FIGS. 4 (a) and 4 (b), when the total content of calcium and magnesium exceeds 5 mg / L during the lapping process, calcium and magnesium are added to fatty acids and nonions contained in the grinding fluid. It is considered that the formation of a surfactant and an insoluble metal salt, etc., and the clogging of the first and second diamond sheets was promoted.

[Comparative Example 3]
Before starting the lapping step, the grinding fluid was diluted with tap water instead of the dilution water, and the total amount of calcium and magnesium in the grinding solution was not controlled during the lapping step, as in Example 1. Then, a glass base plate having compositions 1 to 3 was lapped. The results are shown in FIGS. 4 (a) and 4 (b).

  Specifically, the same tap water as the tap water used in Comparative Example 1 was used, and the same metal ion removal filter as that used in Comparative Example 2 was used. Therefore, the total amount of calcium and magnesium contained in the grinding fluid adjusted before the start of the lapping process exceeded 5 mg / L. And in the glass base plate of composition 1, calcium and magnesium contained in the glass base plate during the lapping step, and in the glass base plate of composition 2, magnesium contained in the glass base plate during the lapping step, respectively. The total amount of calcium and magnesium in the grinding fluid gradually increased (that is, the total amount of calcium and magnesium continuously exceeded 5 mg / L during the lapping process). On the other hand, since the glass base plate of composition 3 contains neither calcium nor magnesium, the total amount of calcium and magnesium in the grinding fluid did not increase even if the total amount of calcium and magnesium was not controlled (however, the lapping process) Inside, there was no change in that the total amount of calcium and magnesium continuously exceeded 5 mg / L).

  From the results of FIGS. 4 (a) and 4 (b), when the total content of calcium and magnesium exceeds 5 mg / L during the lapping step, calcium and magnesium are fatty acids contained in the grinding fluid. It seems that it was further promoted to generate clogging in the first and second diamond sheets by generating an insoluble metal salt with a surface active agent such as or nonionic.

[Comparative Example 4]
Before starting the lapping process, the grinding fluid was diluted with tap water instead of the above dilution water, and the total amount of calcium and magnesium and the amount of cerium in the grinding fluid were not controlled during the lapping process. In the same manner as in Example 1, glass substrates having compositions 1 to 3 were lapped. The results are shown in FIGS. 4 (a) and 4 (b).

  Specifically, the same tap water as that used in Comparative Example 1 was used, and the grinding apparatus was not equipped with a metal ion removal filter. Therefore, the total amount of calcium and magnesium contained in the grinding fluid adjusted before the start of the lapping process exceeded 5 mg / L. And in the glass base plate of composition 1, calcium, magnesium, and cerium contained in the glass base plate during the lapping process, and in the glass base plate of composition 2, magnesium and cerium contained in the glass base plate during the lapping process. However, each appeared in the grinding fluid, and the total amount of calcium and magnesium in the grinding fluid gradually increased (that is, the total amount of calcium and magnesium continuously exceeded 5 mg / L during the lapping process). Further, the amount of cerium in the grinding fluid gradually increased and exceeded 10 mg / L (that is, the amount of cerium exceeded 10 mg / L during the lapping process). On the other hand, since the glass base plate of composition 3 does not contain calcium, magnesium, or cerium, the total amount of calcium and magnesium in the grinding fluid did not increase even though the total amount of calcium and magnesium was not controlled (however, The total amount of calcium and magnesium continuously exceeded 5 mg / L during the lapping process). Further, even if the amount of cerium was not controlled, the amount of cerium in the grinding fluid did not exceed 10 mg / L.

  From the results of FIGS. 4 (a) and 4 (b), when the total content of calcium and magnesium exceeds 5 mg / L during the lapping step, calcium and magnesium are fatty acids contained in the grinding fluid. It seems that it was further promoted to generate clogging in the first and second diamond sheets by generating an insoluble metal salt with a surface active agent such as or nonionic.

  As described above, the present specification discloses various aspects. The main ones of the aspects disclosed in this specification are summarized below.

  One aspect disclosed in the present specification is a method of manufacturing a glass substrate for an information recording medium, which includes a lapping process in which a surface of a glass base plate is lapped using a grinding apparatus including a grinding member and a grinding liquid. In the lapping process, the grinding liquid is lapped so that the total content of calcium and magnesium is always 5 mg / L or less. .

  According to this aspect, since the grinding liquid is lapped so that the total content of calcium and magnesium is always 5 mg / L or less, it is generated from calcium and magnesium and the surfactant in the grinding liquid. Less insoluble metal salt is produced. This reduces the risk of clogging of the grinding member. Therefore, the frequency of dressing of the grinding member can be reduced, and the lapping process can be performed efficiently.

  In addition, since the grinding member is less likely to be clogged, it is possible to suppress the generation of scratches on the ground surface of the glass base plate, and it is possible to suppress the flatness of the ground surface from being deteriorated, which may reduce the quality. Less. In addition, deterioration of the grinding member can be suppressed, and a glass substrate can be manufactured at low cost.

  In another aspect disclosed in the present specification, in the above-described manufacturing method, in the lapping step, the grinding liquid is lapped so that the total content of calcium and magnesium is always 3 mg / L or less. It is characterized by this.

  According to this aspect, it is possible to further prevent clogging of the grinding member by using the grinding fluid while constantly maintaining the total content of calcium and magnesium at 3 mg / L or less.

  Another aspect disclosed in the present specification is characterized in that, in the manufacturing method, in the lapping step, the grinding liquid is lapped so that the cerium content is always 10 mg / L or less. Is.

  According to this embodiment, the grinding liquid is lapped so that the cerium content is always 10 mg / L or less. If the amount of cerium contained in the grinding fluid exceeds 10 mg / L, the grinding member will be clogged, the dressing frequency of the grinding member will be increased, the productivity will be reduced, and the ground surface of the glass base plate will be scratched. Or the flatness of the ground surface deteriorates. Moreover, there is a high risk that the deterioration of the grinding member will be accelerated. Therefore, as in this embodiment, clogging of the grinding member can be suppressed by lapping the grinding fluid so that the cerium content is always 10 mg / L or less. Thereby, the frequency of the dressing process of a grinding member can be lowered | hung and a lapping process can be performed efficiently. Moreover, generation | occurrence | production of the scratch to the grinding surface of a glass base plate can be suppressed, and it can suppress that the flatness of a grinding surface deteriorates. In addition, deterioration of the grinding member can be suppressed, and a glass substrate can be manufactured at low cost.

  Another embodiment disclosed in the present specification is characterized in that, in the manufacturing method, the glass base plate is made of a glass material containing at least one component of calcium and magnesium.

  According to this aspect, the glass base plate is made of a glass material containing at least one component of calcium and magnesium. When the glass base plate, which is the object of lapping, is made of a glass material containing either or both of calcium and magnesium, it is included in the glass base plate during lapping when performing lapping. Calcium and / or magnesium comes into the grinding fluid, and the amount of calcium and magnesium contained in the grinding fluid increases. As a result, the grinding member is easily clogged.

  However, as described above, the total amount of calcium and magnesium in the grinding fluid can be constantly reduced by diluting the grinding fluid with the above dilution water or removing calcium and magnesium from the grinding fluid with a metal ion removal filter. Since it is used at 5 mg / L or less or 3 mg / L or less, clogging of the grinding member is less likely to occur even when lapping a glass base plate made of a glass material containing calcium and / or magnesium components. . Therefore, the method for producing a glass substrate for an information recording medium disclosed in this specification is also suitable for lapping a glass base plate made of a glass material containing at least one component of calcium and magnesium.

  Another aspect disclosed in the present specification is characterized in that, in the manufacturing method, the grinding fluid is diluted with water having a total content of calcium and magnesium of 1 mg / L or less.

  According to this aspect, for example, when the grinding liquid is diluted with water (dilution water) having a total content of calcium and magnesium of 1 mg / L or less before the lapping step, the calcium and magnesium in the grinding liquid The wrapping process can be started from a state where the total content of is very small. Thereby, clogging of the grinding member during the lapping process can be further suppressed, and further deterioration of the grinding member can be further suppressed. Further, for example, when the grinding fluid is diluted with water (dilution water) having a total content of calcium and magnesium of 1 mg / L or less during the lapping process, the glass base plate that is the object of lapping is calcium and magnesium. In the case of a glass material containing one or both of the above components, calcium and magnesium in the grinding fluid can be obtained by diluting with the above water even if calcium or magnesium components appear in the grinding fluid during lapping. The total content can be always maintained at 5 mg / L or less or 3 mg / L or less.

  Another aspect disclosed in the present specification is characterized in that, in the above-described manufacturing method, as the grinding apparatus, a grinding liquid circulation path provided with a metal ion removal filter is used.

  According to this aspect, since a grinding device provided with a metal ion removing filter in the grinding fluid circulation path is used, for example, a glass material that is an object of lapping processing contains calcium, magnesium and / or cerium. Even if calcium, magnesium, or cerium components appear in the grinding fluid during lapping, the total amount of calcium and magnesium in the grinding fluid is always 5 mg / L or less by the above metal ion removal filter. Or 3 mg / L or less, or the cerium content in the grinding fluid can always be maintained at 10 mg / L or less.

  Another embodiment disclosed in the present specification is a glass substrate for an information recording medium manufactured by the above manufacturing method.

  According to this aspect, a glass substrate for an information recording medium in which generation of scratches and reduction in flatness are suppressed can be obtained.

  This application is based on Japanese Patent Application No. 2010-80028 filed in Japan on March 31, 2010, the contents of which are included in this application.

  The present invention provides a method for producing a glass substrate for an information recording medium that is less likely to cause clogging of the grinding member, is efficient, and has a low risk of quality deterioration. For example, an information recording medium such as a hard disk (HD) is provided. A wide range of industrial applicability is expected in the field of manufacturing glass substrates.

Claims (5)

Lapping is performed by lapping the surface of a glass base plate using a grinding apparatus having a grinding member using a grindstone or a diamond sheet and a grinding liquid containing a surfactant capable of generating calcium, magnesium, and an insoluble metal salt. A method for producing a glass substrate for an information recording medium including a step,
As the glass base plate, a glass material containing at least one component of calcium and magnesium is used,
In the lapping step, the grinding liquid is lapped so that the total content of calcium and magnesium is always 5 mg / L or less.   2. The glass substrate for an information recording medium according to claim 1, wherein in the lapping step, the grinding liquid is lapped so that the total content of calcium and magnesium is always 3 mg / L or less. Manufacturing method.   The method for producing a glass substrate for an information recording medium according to claim 1 or 2, wherein in the lapping step, the grinding liquid is lapped so that the cerium content is always 10 mg / L or less. . The said grinding | polishing liquid is diluted with water whose content of calcium and magnesium is 1 mg / L or less in total amount, The manufacturing of the glass substrate for information recording media as described in any one of Claims 1-3 characterized by the above-mentioned. Method. The method for producing a glass substrate for an information recording medium according to any one of claims 1 to 4 , wherein the grinding apparatus is one having a metal ion removal filter in a grinding liquid circulation path.

Images